1. Field of the Invention
The present invention relates to X-ray machines and, more particularly, to a battery operated X-ray machine having an improved circuit arrangement so as to generate intense relatively short pulsed of X-rays. This invention allows for the overall weight of the X-ray machine to be reduced with a corresponding reduction in its physical size so that it more advantageously serves as a portable device.
2. Description of the Prior Art is X-ray machines that generate X-rays from cold field emission of electrons from the cathode of an X-ray tube are commonly employed in pulsed shadowgraph radiographs. Pulsed or flash shadowgraph radiograph was developed in 1938 as a means for observing extremely rapid motion where the subject was obscured from observation with visible light or debris. To date, flash radiography remains the principal means of observing lensed implosions and ballistic impacts over microsecond and nanosecond time scales. The majority of these X-ray systems utilize the well known Marx generator which can be viewed as a distributed transmission-storage line, consisting of n-cascaded high-voltage barium titanate disc capacitors. To produce X-rays, the Marx generator is coupled to a field-emission X-ray tube either directly or by coaxial cables. Coaxial cables provide a low impedance energy store and can be rapidly discharged into the X-ray tube.
When high voltage (H.V.) pulses arrive at the anode of the X-ray tube they establish a large potential gradient in the anode-cathode gap. This gradient produces an intense electric field at the tips of the small metal whiskers which are present on the surface of the cathode mesh. The whiskers are heated by the passage of the field emission electron current and vaporize, creating a neutral plasma which acts as a virtual cathode capable of supporting a much larger current. Electrons emitted from the expanding virtual cathode are accelerated by the electric field in the anode-cathode gap and eventually collide with the anode creating X-rays by the usual Bremmstrahlung and line radiation processes. Electrons continue to cross the anode-cathode gap until the expanding cathode plasma reaches the anode at which time the X-ray tube impedance drops to a few ohms and effectively shorts the tube.
While Marx generator driven X-ray systems have worked well in the past, they have employed large transformer-rectifier high voltage power supplies for charging the Marx capacitors and generally use heavy coaxial cables to couple the Marx generator to the X-ray tube. The heavy coaxial cables act to sharpen the high voltage pulses produced by the Marx generator but, the physically large bundle of cables disadvantageously adds to the weight of the X-ray machine so as to hinder its portability. Further more, the heavy high voltage power supply also disadvantageously contributed to the weight of the X-ray machine while also hindering its maneuverability. It is desired that a means be provided that reduce the overall weight of the X-ray machine, while also eliminating the need for the heavy coaxial cables with both features contributing to an X-ray unit that is truly portable. More particularly, it is desired that a compact and portable design for X-ray machines be provided so that the X-ray machine may advantageously be used in remote locations, as in X-ray imaging devices for medical diagnostics and also for triage related to medical disasters.